[Antennas] Would vertical be better than yagi? Maybe...

2002年6月11日 17:55:58 -0500

Actually, John, if you look at the elevation patterns ("take-off angle")
of a Yagi antenna, you'll find that the take-off angle of a Yagi is the same
as a dipole at the same height! The major difference is that the Yagi has
(usually) a front-to-back and front-to-side ratio that the dipole *doesn't*
have,
and that's why it produces "gain" over the dipole.
Your particular "... lack of height..." is why your Yagi is not performing
as
expected.
If you'll read the appropriate sections of the ARRL "Handbook" or the
ARRL "Antenna Book", you'll begin to understand the importance of
height above ground for *any* antenna, and how it affects the radiation
pattern, the "take-off angle" and so on......
Karl K - W8TIF
McKinney, Texas
-----Original Message-----
From: John Geiger
Sent: Tuesday, June 11, 2002 3:04 PM
To: [email protected]; [email protected]; [email protected]
Subject: would vertical be better than yagi?
I recently put up a 2 element triband yagi (full size
tribander) but it is not up very high-maybe 25 feet or
so. The lack of height is noticable in performance.
It does show gain towards Europe vs my dipole (G5RV
type, also not up very high), and it also showed gain
over the dipole when working VK9LO the other day.
SOmetimes the yagi is a couple of S units better than
the dipole towards Europe. Most of this has been done
on 20 meters. Have not found enough stuff on 10 to
compare yet.
However, the past few days been trying to work BQ9P
for #298, and the yagi doesn't show much gain at all
over the dipole towards the far east-observe the same
with Japan. Did work DU3NXE on 20 cw this AM with the
yagi, but he was about as loud on the dipole.
THe way I understand it, the low height does not give
me the low angle radiation lobes that the long haul DX
often requires. So my question is: Given that I
might not be able to get the Yagi much higher for some
time (my yard is a nightmare of trees and power lines)
would I be better off getting a vertical on the roof
instead. I know that verticals hear equally poor in
all directions, but would it allow me to get the lower
angle-long haul stuff.
I would appreciate any comments, especially from those
who have been in the same boat.
73s John NE0P